Process for reducing error in the sampling of materials



United States Patent 3 392,587 PROCESS FOR REiJUCING ERROR IN THE SAMPLING OF MATERIALS Pierre M. Gy, Paris, France, assignor to Minerais et 3,392,587 Patented July 16, 1968 lar equal time periods another lesser time period made up from a random number of time units.

This process applies to the sampling of materials in substantially continuous transport. Transportation is ef- Metaux, Paris, France, a society of Flame 5 fected by sliding stop-valve pumps, slide-type distributors, No Drawing Filed July 6 1966, sen 563,072 vibrating chutes, etc.; generally speaking, it extends to Claims Priority, application France July 6 1965, the sampling of any material during the course of its 2 1 transport, the heterogeneousness of said material being 1 Claim. (Cl. 73-421) affected by one of several cyclic phenomena, and more 10 particularly when the periods of these phenomena may vary. ABSTRACT OF THE DISCLOSURE The following description comprises a certain number A process for sampling materials while continuously or of embodlmellts s Y for illustrativ? P PP to Point eemieontinuously transporting the materials for reducing out the characteristics of the present lnvention as well as sampling errors due to cyclic variations in the pro t the numerous forms of application of the process which of the material being sampled is accomplished by taking 15 the oblect of the mventl'om the samples at irregular intervals. The irregular intervals For example, let us examine a device which effects are obtained by adding to a series of equal time periods samplings of materials at the delivery end of a conveyor additional time units corresponding to one of a series of or of a feeding device: mill-hopper or loading funnel, random numbers, the additional time units being less than spout or shoot, etc., and in which the sampling tool is each time period for the purpose of selecting the samactuated with a linear reciprocating discontinuous motion pling time. actuated by an appropriate mechanism. Experience shows that under such conditions, the measures taken during t the regular sampling often reveal a certain periodicity. Present lnventlon relates to a nevi/Process for the 29 According to this invention, the sizeable sampling er- SamP1 1ng 'f of m and partlculfifly battchfis rors resulting from the coincidence of the sampling and of sohd or liquid materials or mixtures of solid and liquid f the ff t due to the periodieity thuS revealed are materials, dUf1I 1g the CQUFSE 0f the traflspol'l, Wlth the eliminated by effecting the samplings not at regular interl f 0f reduclng the $126 0f Sampllng error 30 vals, but at time intervals set at random, with respect to It 15 known that the properties of a sample tak n f the average time interval separating the various conseca batch of heterogeneous material may be different from utive samphngS the corresponding properties of the batch itself, this diifer- As an example, in washing Ore, it is desired tO obtain, ence constituting the sampling error. At the present tlme during the course of an 8410 shift, a sampling i g i of i g g i posed of 48 elementary samplings. According to the inf y mg e O a OW 0 ma ena or a cervention, a regular sampling every ten minutes is not eftam period of time at regular intervals. It has been found faded but a Sam tin di tributed at random with. ch that the sampling error is considerable when properties f 1 t Th m 3 of the material being sampled are subject to variations 0 b l mtelva S i a f f of a cyclic character. These cyclic variations are very Ftratlfied dlstflbutlon can be obtamed h as Elven f t They may be due t0 the apparatus effecting the 40 m the following table for the first 20 samplings:

Sampling Position Time since Sampling Position Time since number in stratum start number in stratum start .5mn.30 l1 Qmn 1h.42mn. 13 mn. 30 56 mn. 22 mn 2 mn. .30 Inn. 30 16 mn. 30. 46 mn. 30 25 mn. 53 mn 38 mn. 6 mn 40 mn. 17 Inn. 30 53 mn. .23 mn 6 mn. 30. .38 mn. 30 17 Inn. 30.

transport of the material, such as pumps, slide-type distributors, etc. Such variations exist also each time that the treatment of the material comprises circulating loads, i.e., each time that all or a portion of the material must be subjected to a new cycle of preparation or transformation. For example, for ore, returning to the crushing mill all portions rejected during the course of a screening or grading operation. However, the cyclic variations are often difficult to pinpoint and characterize, particularly since the period of these variations is itself susceptible of variation Within certain limits. Thus it may occur that the sampling period coincides with the period of these variations, which then causes a considerable sampling error.

The object of the present invention is, therefore, to eliminate the substantial sampling errors due to this cyclic phenomenon effecting the sampling of materials, in such a manner that the time intervals between two samplings is not constant, but on the contrary variable, the sequence of these time intervals being obtained by adding to regu- To this effect, the random distribution is obtained by means of any table of numbers selected at random. It is possible, for example, to take the first 48 two-figure numbers found in such a table comprised between 0 and 19, limits included, keeping the repetitions.

If we take as unit of time the half-minute, these numbers define the position of the sampling in each of the l0-minutestrata. Thus a random fluctuation is obtained around an average time of 10 minutes.

One of the advantages of the process resides in the fairly uniform distribution of the samplings taken at variable intervals determined by adding a. random number of time units to regular time period, over the whole sampling period, while in a distribution taken completely at random, the samplings could be bunched up in small groups separated by very long time intervals.

The process which is the object of the invention is carried out by determining the time intervals selected in accordance with said process, by means of any reference mark carried on supporting means. The detection of thesereference marks is effected by means of any appropriate reading device. An eventual amplification of the signal controls the start of the sampling operation as well as the emission of any other desired signal.

According to a first type of embodiment, a disc carries the reference marks, which are, for example, conducting marks susceptible of closing the circuit triggering the actuation of the sampling device each time one of these marks passes in front of the detection device. In the example considered, in which 48 samples are to be taken at the time intervals shown on the above table, we select a non-conducting disc, actuated by a motor rotating at a constant speed, making one turn in 8 hours, and in which the guide marks are distributed over a circumference of 306 mn., in such a manner that a distance of one millimeter of circumference run corresponds to a time of 30 seconds.

Thus forty-eight reference marks corresponding to the forty eight samplings indicated in the above mentioned table, are made on the circumference at distances which are proportional to the time intervals shown in the third column of the table.

As soon as one of these reference marks constituted by a conducting mark is detected by the reading device, two conducting plates, for example, an electric signal permits to actuate, either directly the device triggering the sampling mechanism, or the intermediary relay station which then triggers said mechanism.

It is clear that the reference marks may also be constituted by a metallic mass which is capable of being detected by a variation of the magnetic field.

It is also possible to create the reference marks by perforations distributed at random, as has just been indicated along a circumference next to the edge of a disc.

A general switch permits, when it is put in service, connection of the feeding system to a synchronous motor effecting, for example, one turn in eight hours. The starting of the synchronous motor therefore actuates the rotation of the disc, the perforations of said disc passing be tween a device which supplies a light beam and a photocell. The closing of the general switch also actuates the lighting device, comprising, for example, an exciter or exciting dynamo, the light radiation being directed by a reflecting prism onto a precise point in such a manner that when a perforation of the disc passes under a photocell, the latter receives the totality of the light reflected by the prism. The exciter is connected to a transformer actuated by the closing of the main switch. An electronic amplifier placed in parallel with the preceding transformer is connected to the photocell and transmits through its outlet the voltage necessary to excite the coil of the contactor of the motor which actuates the sampling tool.

According to another embodiment of the invention, the reference marks may be replaced by magnetic recordings made either on record or on magnetic tape or drum.

Such recordings may be made directly from an electronic computer. It is possible, of course, as in the embodiment that has just been described, to run the tape at a low speed, the reading device then being conceived to detect the magnetic marks practically at no speed. It is also possible to use a tape which runs at the speed of the apparatus connected to the electronic computer. In this case, it is advantageous, according to the invention, to use an endless magnetic tape and to have magnetic marks distributed at random around regular intervals. Since the endless tape may be run several times, the order in which the marks must be detected may be numbered and the reading speed of the tape must be reduced in a suitable manner. The process to calculate the intervals taken at random may be of any type.

Although only two embodiments of the invention have been described for illustrative purposes, it would be within the scope of the invention to replace the guide marks made on disc or tape by reference marks of another nature made on other supports. It is also possible to use as reference marks transparent or opaque marks detected by photoelectric cells during the running of an opaque or transparent tape.

These tapes may also be replaced by perforated tapes which run at a constant speed in front of an electric reading feeler.

Finally, it is clear that it is within the scope of the invention to stop systematically the tape after each detection for a fixed period of time, which is equal at the most to the minimum interval separating two samplings, which permits to reduce in certain cases the length of the tapes used for the control of the samplings.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

I claim:

1. A process for sampling materials while substantially continuously transporting the materials to reduce sampling errors due to cyclic variation in the properties of the material being sampled by effecting the samplings at irregular intervals, with the improvement comprising: taking a sample during one of a plurality of equal and uniform time periods, the time of sampling within said one time period being determined by assigning each of a plurality of smaller time units within each time period a number and taking the sample in said one time period at the expiration of a time unit whose number corresponds to one of a series of random numbers, taking a sample during a second time period at the expiration of the time unit in the second time period whose number corresponds to another number in the series of random numbers used to determine the time of sampling within the first time period.

References Cited UNITED STATES PATENTS 2,622,282 12/1952 Hare 73-423 X DAVID SCHONBERG, Primary Examiner.

S. CLEMENT SWISHER, Examiner. 

